This invention relates generally to alarm systems for motor vehicles and more specifically to alarm systems employing radio speakers for acoustical signal emission.
Alarm systems for motor vehicles employing radio speakers for sound emission are disclosed for example in German DE-OS No. 23 42 121. It is also generally known (for example, as disclosed in German DE-OS No. 32 35 071) to arrange the speaker systems used in automobiles on or under horizontal depositing surfaces in front of the rear window and/or in front dashboard panels behind the windshield. The axis of the speaker extends essentially vertically with respect to the horizontally arranged depositing surface or dashboard panel. This installation position has proven to be advantageous because the interior of the vehicle receives exposure to sound waves during operation of a radio or tape player which is enhanced by tne reflection of the sound waves at the front or rear window as well as at the ceiling of the vehicle. However, in order to meet individual demands, it has been proposed in German DE OS No. 20 53 038, DE-OS No. 31 11 078 and DE-Gbm No. 16 54 582 to rotatably and/or pivotably mount a speaker in a motor vehicle in such a way that the direction of the sound can be changed by manual adjustment.
When a speaker system is used for radio or tape player acoustic signal emission in connection with a motor vehicle alarm system, such as a warning system for unauthorized intrusion or theft, the arrangement of the speakers is primarily aimed at exposure of the vehicle interior to sound waves. Due to this arrangement, primarily designed for optimum sound emission in the vehicle interior, the level of alarm sound emission reaching the outside of the vehicle is not optimized.
Accordingly, it is an objective of the present invention to develop an alarm system of the above general type wherein the speaker additionally provides optimum sound emission when employed in a vehicle alarm system.
This and other objectives of the present invention are obtained by the provision of an alarm system for motor vehicles which employs at least one radio speaker installed in the vehicle for the purpose of generating an acoustic signal which is transmitted to the outside of the vehicle. The transmission of the acoustic alarm signal to the outside of the vehicle is improved in accordance with the present invention by providing a control element which swivels the speaker from its normal installed position into a position parallel with an external surface of the motor vehicle. In a preferred embodiment, the speaker is swivelled from a position parallel with a horizontal surface adjacent a vehicle window so that the surface of the speaker becomes parallel to the plane of the adjacent window. Alternatively, a speaker mounted in a vehicle door can be swivelled into a position parallel or nearly parallel witn respect to the outer surface of the vehicle door.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.